The present invention relates to disc drive data storage systems and, more particularly, to the use of microactuators in disc drive head positioning apparatus.
Disc drive data storage systems use rigid discs which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective disc head sliders. The sliders carry transducers which write information to and read information from the disc surfaces. The slider and transducer are often together referred to as a xe2x80x9cheadxe2x80x9d. Each slider is supported by an actuator arm and a suspension. The actuator arms move the sliders from track-to-track across the surfaces of the discs under the control of electronic control circuitry for track following operations.
The suspension connects the actuator arm to the slider. The suspension provides a preload force through a relatively rigid load beam which forces the slider toward the disc surface. Additionally, the suspension is flexible in the slider pitch and roll directions to allow the slider to follow the topography of the disc. This pitch and roll flexibility is obtained from a gimbal or flexure structure, which can be integral with the load beam or a separate piece part that is welded or otherwise attached to the load beam.
The slider includes a hydrodynamic (e.g., air) bearing surface, which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the bearing surface. As the air passes beneath the bearing surface, air compression along the air flow path causes the air pressure between the disc and the bearing surface to increase, which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to fly above or in close proximity to the disc surface. It is desirable to maintain a substantially constant flying height during read and write operations.
Two major mechanical challenges facing the designers of disc drives include accurate servo track following operations in disc drives having ultra high track densities and limiting flying height variations during different operating conditions and between different sliders, especially in disc drives having ultra-low fly heights. Disc drive manufacturers are nearing the limits of their ability to ensure close track-following with conventional single-stage actuators, such as actuators employing voice coil motors. This is due to structural resonances and disturbances present in the disc drive. One method of dealing with these structural resonances and disturbances is through the use of a second stage xe2x80x9cmicroactuatorxe2x80x9d, which is located closer to the transducer than the voice coil motor and thereby excludes many of the structural resonances between the microactuator and the voice coil motor. Performance, manufacturability and cost are three main challenges in implementing microactuators.
With respect to limiting variations in flying heights, currently flying heights are entering the nanometer range. Any factors causing variations in the flying heights of sliders are therefore becoming more significant and difficult to control. Excessive flying height variation, both for a given head under different operating conditions and for the population of heads manufactured, can confound the ability of the disc drive to read and write properly.
The present invention provides a solution to this and other problems and offers other advantages over the prior art.
One embodiment of the present invention relates to a dual-acting disc drive microactuator formed of a stack of adjoining layers, which includes first through fifth layers. The first layer includes first and second spaced apart top electrodes. The second layer includes a first piezoelectric element electrically coupled to the first and second top electrodes. The third layer includes a center electrode electrically coupled to the first piezoelectric element. The fourth layer includes a second piezoelectric element electrically coupled to the center electrode. The fifth layer includes a first bottom electrode electrically coupled to the second piezoelectric element. The first and second piezoelectric elements are expandable and contractible in a common length direction in response to respective electrical fields applied between the center electrode and the first top electrode, the second top electrode and the first bottom electrode.
Another embodiment of the present invention relates to a disc drive suspension having a longitudinal axis, a transverse axis and an elongated stack of adjoining layers, which extends along the longitudinal axis and includes first through fifth layers. The first layer includes first and second coplanar top electrodes which are separated from one another along the transverse axis. The second layer includes a first piezoelectric element which is electrically coupled to the first and second top electrodes. The third layer includes a center electrode which is electrically coupled to the first piezoelectric element. The fourth layer includes a second piezoelectric element electrically coupled to the center electrode. The fifth layer includes a first bottom electrode electrically coupled to the second piezoelectric element. The first and second piezoelectric elements are expandable and contractible along the longitudinal axis in response to respective electrical fields applied between the center electrode and the first top electrode, the second top electrode and the first bottom electrode.
Another embodiment of the present invention relates to a disc drive including a disc, which is rotatable about a central axis, and a suspension for carrying a transducer relative to the disc. The suspension has a dual-acting piezoelectric bimorph element which deforms a section of the suspension in a cross-track direction and in a vertical direction relative to the disc in response to electric fields applied to the bimorph element.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading the following detailed description and review of the associated drawings.